1,2-Diphenylhydrazine

122-66-7

Hazard Summary-Created in April 1992; Revised in January 2000

1,2-Diphenylhydrazine was used in the past to produce benzidine-based
dyes. Currently, the only use for it in the United States is in
the production of anti-inflammatory drugs. Limited information is
available on the health effects of 1,2-diphenylhydrazine. No information
is available on the acute (short-term), chronic (long-term), reproductive,
developmental, or carcinogenic effects of 1,2-diphenylhydrazine in humans.
In a National Cancer Institute (NCI) study, liver tumors were observed
in both sexes of rats and female mice exposed to 1,2-diphenylhydrazine
in their diet. EPA has classified 1,2-diphenylhydrazine as a Group B2,
probable human carcinogen.

Uses

1,2-Diphenylhydrazine is used as a starting material in the production
of benzidine. Benzidine was used in the past to manufacture benzidine-based
dyes which are no longer used in the United States, but may still be
used in other countries. (1)

1,2-Diphenylhydrazine is used in the production of anti-inflammatory
drugs. (1)

Sources and Potential Exposure

Human exposure to 1,2-diphenylhydrazine appears to be primarily occupational;
however, the number of workers potentially exposed has declined because
dye manufacturers in the United States no longer produce benzidine-based
dyes. (1)

Assessing Personal Exposure

There is no test currently available to determine whether or not
exposure to 1,2-diphenylhydrazine has occurred. (1)

Health Hazard Information

Acute Effects:

No information is available on the acute effects of 1,2-diphenylhydrazine
in humans or animals.

Chronic Effects (Noncancer):

No information is available on the chronic effects of 1,2-diphenylhydrazine
in humans. No inhalation data are available in animals.

Degenerative alterations in the liver and depressed weight gain have
been observed in rats and mice chronically exposed to 1,2-diphenylhydrazine
in their diet. (1,2,4)

Intestinal hemorrhage in mice and stomach hyperkeratosis and acanthosis
in rats has been observed when the rodents were chronically exposed
to 1,2-diphenylhydrazine in their diet. (1,2,4)

Chronic oral administration of 1,2-diphenylhydrazine produced interstitial
inflammation of the lungs in rats. (1)

EPA has not established a Reference Concentration (RfC)
or a Reference Dose (RfD) for
1,2-diphenylhydrazine. (3)

Reproductive/Developmental Effects:

No information is available on the reproductive or developmental
effects of 1,2-diphenylhydrazine in humans.

In one study, no effects on reproductive organs were found in rats
and mice exposed via ingestion. (1)

Cancer Risk:

No information is available on the carcinogenic effects of 1,2-diphenylhydrazine
in humans.

In an NCI study, hepatocellular carcinomas were observed in both
sexes of rats and female mice exposed to 1,2-diphenylhydrazine in their
diet; mammary adenocarcinomas were also observed in female rats. (3,4)

EPA has classified 1,2-diphenylhydrazine as a Group B2, probable
human carcinogen. (3)

EPA uses mathematical models, based on human and animal studies,
to estimate the probability of a person developing cancer from breathing
air containing a specified concentration of a chemical. EPA calculated
an inhalation unit risk estimate of 2.2 × 10-4 (µg/m3)-1.
EPA estimates that, if an individual were to continuously breathe air
containing 1,2-diphenylhydrazine at an average of 0.005 µg/m3
(0.000005 mg/m3) over his or her entire lifetime, that
person would theoretically have no more than a one-in-a-million increased
chance of developing cancer as a direct result of breathing air containing
this chemical. Similarly, EPA estimates that breathing air containing
0.05 µg/m3 (0.00005 mg/m3) would result
in not greater than a one-in-a-hundred thousand increased chance of
developing cancer, and air containing 0.5 µg/m3 (0.0005
mg/m3) would result in not greater than a one-in-ten thousand
increased chance of developing cancer. For a detailed discussion of
confidence in the potency estimates, please see IRIS. (3)

Note: There are very few health numbers or regulatory/advisory numbers
for 1,2-diphenylhydrazine; thus, a graph has not been prepared for this
compound. The health information cited in this fact sheet was obtained in
December 1999.

National Cancer Institute. Bioassay of Hydrazobenzene
for Possible Carcinogenicity (CAS No. 122-66-7). TR-92. U.S. Department
of Health, Education, and Welfare, Public Health Service, National Institutes
of Health. 1978.